Asthma is a common disease that is characterized by an episodic narrowing of the airways. It is a major public health concern that affects about 23 million adults in the United States. Infiltration of activated eosinophils into the bronchioli is believed to be a primary cause of asthma. Eosinophil counts and the presence of secreted eosinophil granular proteins such as Eosinophil Peroxidase (EPO) in sputum and lung biopsy samples are indicators of the severity of asthma. Bromotyrosine protein modifications are increased in asthma patients due to EPO, which catalyzes the formation of hypobromite and the subsequent formation of bromotyrosine. Previous studies that used gas chromatography with mass spectrometric detection found that 3-bromotyrosine and 3,5-dibromotyrosine were significantly elevated in bronchoalveolar lavage fluid and sputum samples from asthmatics, respectively. Studies on the role of brominated proteins in asthma have been limited by the lack of a rapid, simple method to monitor bromotyrosine levels in biofluids.